1. Field of the Invention
This invention relates to a spring hinge for eyeglasses in which each bow can be swung out against spring force about a fulcrum spaced from the hinge axis so that the bow will resiliently bear on the head of the wearer.
2. Description of the Prior Art
A spring hinge for use in such eyeglasses is known, e.g., from German Patent specification No. 11 24 727 and comprises a bow-side hinge member to be connected to a bow, a rim-side hinge member to be connected to the rim of the eyeglasses, and a hinge pin pivotally connecting said hinge members. The bow-side hinge member is connected to a spring-loaded plunger, which is slidably mounted in a receptacle and is adapted to be pulled out of the receptacle against the force of a coil spring, which tends to retract the plunger and is slidably fitted on a rod of the plunger, and the spring bears at one end on a head of the plunger. To assemble that spring hinge as well as the spring hinge disclosed in French Patent specification No. 78 07 553, access to opposite ends of the receptacle is required and in the known spring hinges the second abutment for the spring is constituted by a shoulder formed in said receptacle. That assembly and design are expensive and require a special shape and a relatively large bulk of the receptacle, which is connected to the bow.
Other spring hinges, such as the one disclosed in German Patent specification No. 12 35 623, comprise a spring-loaded pin, which extends at right angles to the longitudinal axis of the bow and are highly expensive and cannot be used with the thin, metal frames which are often used now and comprise also thin metal bows.